In recent years, semiconductor packages having high insulating properties and good heat radiating properties have become required in semiconductor modules that are provided with a power semiconductor element, such as an IGBT (Insulated Gate Bipolar Transistor) and power MOSFET. One means for achieving a semiconductor package of this kind is a semiconductor module having an integrated high-thermal-conductivity insulating sheet structure (see, for example, PTLs 1 and 2).